Paul Nicholls hailed Kauto Star a “once in a lifetime” horse after the dual Cheltenham Gold Cup winner had to be put down due to injuries sustained in a paddock accident.

The 15-year-old enjoyed a glittering career with the champion trainer after being bought from France as a four-year-old, most notably winning the King George VI Chase at Kempton five times and becoming the first horse to regain the Cheltenham Gold Cup.

He retired from racing after pulling up in the 2012 renewal of the blue riband having won 23 of his 41 races and over £2.3million in win and place prize-money.

Later that year Kauto Star went on to pursue a career in dressage with Laura Collett, a decision which led to a breakdown in relations between Nicholls and owner Clive Smith.

Nicholls revealed he only learned of Kauto Star’s injuries and euthanisation earlier today.

“Laura Collett kindly called me before there was a press release this morning.

“That’s the first I knew about it, although I understand the accident happened nearly a week ago,” said the champion trainer.

“It’s obviously a very sad day and very sad news to take on board. I’m obviously mortified.

“He was like my best mate really. I saw him every day and he was a great horse in every way temperament-wise.

“When he left, it was obviously a big hole we had to fill in everybody’s lives. He’d been so good for racing and so good for everybody.

“When something like this happens it’s awfully sad, but sometimes things are unavoidable.

“It hasn’t really sunk in, to be honest. Everyone is very upset.

“It’s happened and we’ve all got to get on.

“He was very sharp, not always easy to deal with and he had his own way of doing things, but he was just a brilliant horse and from day one he was always going to be very classy.”